The present invention relates to a method and system for authenticating an individual by using a biometrical feature that the individual has.
The biometric authentication is known as an authentication technique having an advantage that there is no forgetting and forgery is difficult as compared with authentication based on a password or a Smart card. In the biometric authentication, biometric information is acquired from a user (hereafter referred to as enrollee) and information called feature is extracted from the biometric information and registered, at time of registration. This registration information is called registered template. At time of authentication, a feature extracted from a user (hereafter referred to as authentication object user) is matched with the template, and authentication is conducted by using an obtained similarity which represents how alike two feature are or an obtained score representing a distance which represents how different two feature are (hereafter referred to as score).
Biometric authentication in which the authentication object user is matched with each of N enrollees (hereafter referred to as 1:N matching) to identify which of the enrollees is the same person as the authentication object user is called 1:N biometric identification. It at this time there is an enrollee (hereafter referred to as identified enrollee) identified as the same person as the authentication object user, then the authentication is regarded as successful with the identified enrollee obtained as an identification result. If there isn't an identified enrollee, then the authentication is regarded as unsuccessful. As examples of a biometric authentication system utilizing the 1:N identification, a service record management system and a system for conducting credit account settlement on the basis of biometric authentication without using a credit card (hereafter referred to as card-less credit account settlement system) can be mentioned. The 1:N identification has an advantage of high convenience because the authentication object user need not exhibit a card or the like. However, the 1:N identification has a problem that as the number N of enrollees increases the authentication accuracy is degraded and the authentication time increases because the number of identification objects increases.
According to K. Nandakumar. et al., “Fusion in Multibiometric Identification Systems: What about the Missing Data?,” Proc. ICB, pp. 743-752, 2009 (Document 1), in the 1:N identification, a posterior probability that the authentication object user will be each enrollee is calculated on the basis of obtained scores and the user is identified by using the posterior probability.
According to JP-A-H11-296531 ([0008], [0012], FIG. 1, Document 2), which corresponds to U.S. Pat. No. 6,229,922 B1, Sasakawa et al., a similarity table using similarities each of which is a degree of coincidence between two registered data obtained by calculating it for all possible combinations in selecting two out of a plurality of registered data is generated beforehand, and a sequence of registered data to be read subsequently is controlled by using a matching degree between matching data to be matched and registered data and the similarity table. At this time, it is also possible to discontinue the matching processing if the number of times of matching exceeds a predetermined threshold.